1. Field of the Invention
The present invention relates to a memory controller, a flash memory system having the memory controller, and a control method of a flash memory.
2. Description of the Related Art
In recent years, the performances (storage capacity, reliance, operation speed, etc.) of flash memories have been improving. Therefore, it is happening that the flash memories are used for the purposes of storing programs, etc., as non-volatile storage media.
The flash memories have a risk that the data read out therefrom might include errors, due to its own characteristic. Raised as one cause for the risk is the disturb phenomenon described in, for example, Unexamined Japanese Patent Application KOKAI Publication No. 2004-272476, page 4. The disturb phenomenon is a phenomenon that when reading or writing is performed on a memory cell, the state of other memory cells that use a bit line in common with that memory cell is changed. In some cases, the disturb phenomenon causes data once written, to change over time to invite errors to mix in the data.
Thus, in a case where it is intended that an activator program (boot program) stored in a flash memory be executed when an apparatus using the flash memory as its storage medium is turned on, the program sometimes cannot be executed properly and the apparatus therefore cannot be activated.